#include<fstream>
#include<algorithm>
using namespace std ; 
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
int Cauta(int n , int v[] , int target ){
    
      int st =1  , dr = n ; 
      while(st<=dr){
           int mij = (st+dr)/2;
             if(v[mij] <= target ){
                  
                   
                 st = mij + 1 ; 
             }else  {
                   dr = mij -1 ; 
             }
      }

    return st; 

}
int main(){

     int v[100001]  , n , cnt =0 ; 
       cin>>n;
         for(int i = 1 ; i <= n ; i ++ )
            cin>>v[i];
        sort(v+1,v+n+1);
    
          for(int i = 1 ; i <= n - 2  ; i ++ ){
               for(int j = i + 1 ; j <= n - 1 ; j ++ )
                 {
                     int temp = Cauta(n,v,v[i]+v[j]);
                     
                        cnt +=temp-j -1; 
                 }
          }
cout<<cnt;





    return 0 ; 
}